Substituted styrenes

ABSTRACT

Certain substituted styrenes are prepared by dehydrohalogenating certain halogen-substituted phenyl ethanes using as the dehydrohalogenating reagent an amine acceptor of the generic formula:   WHEREIN R is an alkyl group of 1 to 6 carbon atoms, n is an integer having a value of from 1 to 5, and at least one alkyl group is attached to a carbon atom adjacent to the nitrogen atom and when n is more than 1, the alkyl groups may be the same or different groups.

United States Patent [1 1 Bianchi Dec. 16, 1975 1 SUBSTITUTED STYRENES [75] lnventor: Thomas A. Biahchi, lrondequoit,

[73] Assignee: Eastman Kodak Company,

Rochester, NY.

[22.] Filed: Aug. 24, 1973 [211 App]. No.: 391,180

Related US. Application Data [63] Continuation-impart of Ser. No. 237.902. March 24,

1972, abandoned.

[52] US. CL... 260/613 D; 260/651 R; 260/651 HA [51] Int. Cl. C07C 41/00 [58] Field of Search 260/669 R, 669 OZ, 613 D [56] References Cited UNlTED STATES PATENTS 2.877,227 3/1959 Cohen ct a1. 260/613 D X 2,916,521 12/1959 Longlcy 260/613 D OTHER PUBLICATIONS Sulzbacher. Jour. Applied Chem., V01. (1951), pp.

Primary Examiner-Bernard Helfin Attorney, Agent, or FirmE. W. Milan 5 7 ABSTRACT Certain substituted styrenes are prepared by dehydrohalogenating certain halogen-substituted phenyl ethanes using as the dehydrohalogenating reagent an amine acceptor of the generic formula:

10 Claims, N0 Drawings SUBSTITUTED STYRENES This is a continuation-in-part of US. application Ser.

No. 237.902, filed Mar. 24, 1972 and now abandoned.

FIELD OF THE INVENTION BACKGROUND OF THE INVENTION It has been proposed that 3.4-dialkoxy styrenes (substituted styrenes) be prepared by dehydrohalogenating chloro-l-(3,4-dialkoxyphenyl)ethanes using pyridine as the dehydrohalogenating reagent. In the prior art, 3,4-(dimethoxy) styrenes have also been prepared by the thermal dehydration of l-(3,4-dimethoxyphenyl)ethanol and by methylation of 4hydroxy-3-methoxy styrene with methyl iodide or dimethyl sulfate. These methods have not been entirely satisfactory because the yields are rather low. Very low yields are obtained in the dehydrohalogenation process because of the formation of the quaternary salt of pyridine with the chloro compound. The thermal dehydration process is also relatively expensive because of the high temperature required for the reaction.

It has also been proposed that haloalkyl styrenes be prepared by at least partially dehydrohalogenating halogenated haloalkylphenyl ethanes using pyridine as the dehydrohalogenating reagent. These styrenes have also been prepared by haloalkylating styrene. The same disadvantages that the use of pyridine presents in its use in preparing dialkoxy styrenes occur in such methods.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for preparing substituted styrenes in improved yields. Another object of the present invention is to provide a process for making 3,4-(dialkoxy) styrenes and haloalkyl styrenes at improved yields. A further object of this invention is to provide reagents for dehydrohalogenating halogenated l-(dialkoxyphenyl)ethane. A still further object of the present invention is to provide reagents for dehydrohalogenating halogenated haloalkylphenyl ethanes. An additional object of this invention is to provide a process for preparing 3,4-(dimethoxy)styrene. A further object of the present invention is to provide a process for preparing chloromethylstyrene, and especially p-chloromethylstyrene.

These and other objects and advantages of this invention are obtained by dehydrohalogenating halogenated l-(dialkoxyphenyl)ethane or a halogenated haloalkylphenyl ethane using as the dehydrohalogenating reagent an amine acceptor of the generic formula:

wherein R is an alkyl group of l to 6 carbon atoms, n is an integer having a value of from 1 to 5, and at least one alkyl group is attached to a carbon atom adjacent to the nitrogen atom and when n is more than 1, the alkyl groups may be the same or different groups.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The substituted styrenes prepared according to the process of this invention correspond to the following formulae I and Il:

wherein each R is an alkyl radical of l to 4 carbon atoms and preferably methyl;

\ CH=CH wherein R is an alkylene radical of l to 4 carbon atoms and preferably methylene, and X is a halogen atom selected from the group consisting of chlorine, bromine, and iodine, and preferably is chlorine.

In a stepwise method of preparation of the substituted styrenes, a l-(3,4-dialkoxyphenyl)ethanol wherein each alkoxy moiety has 1 to 4 carbon atoms may be used as a starting material to prepare a compound of formula I. In the preferred embodiment, 1- (3,4-dimethoxyphenyl)ethanol is used. The starting material is converted in step (1) to its intermediate halogen derivative by reacting it with a suitable halogenating agent. Suitable halogenating agents are, for example, in chlorination, thionyl chloride; in bromination, hydrogen bromide, thionyl bromide, or phosphorus tribromide; in iodination, the standard iodinating agents, e.g. I For example, I-(3,4-dimethoxyphenyl)ethane is converted to l-chloro-l-(3,4-dimethoxyphenyl)ethane by reaction with thionyl chloride.

The halogen derivative is then in step (2) dehydrohalogenated by reaction with an amine acceptor of the generic formula:

wherein R is an alkyl group of l to 6 carbon atoms, n is an integer having a value of from 1 to 5, and at least one alkyl group is attached to a carbon atom closest to the nitrogen atom and when n is more than 1, the alkyl groups may be the same or different groups, as the dehydrohalogenating reagent to prepare the formula I compound.

Examples of amine acceptors according to this generic formula are 2,6-lutidine, s-collidine, and 2-picoline. Preferably. an excess of the amine acceptor is used to keep the reaction basic throughout, thereby avoiding the risk of polymerization which takes place in the presence of acid. Other suitable materials may be used to keep the reaction basic.

Preferably, the dialkoxy compound is treated in a process wherein steps l) and (2) are combined and the dialkoxy compound, the halogenating agent, and

the amine acceptor are all placed in the same container In the method of preparation of the substituted styat the same time. Thus, in the preferred reaction, the renes of formula II, an alkyl benzene, wherein the alkyl dialkoxy compound is treated in such a combination group has 1 to 6 carbon atoms, may be used as a startprocess with thionyl chloride in the presence of two ing material. In the preferred embodiment it is ethyl molar equivalents of 2,6-lutidine. The dialkoxy combenzene. The starting material is converted in step (1) pound is thus converted to the intermediate halogen to its halogen derivative in a stepwise process by reactderivative, the chloro derivative in the preferred reacg the a kyl e e With 8 mixture 0fPa1'a-f0rmalde tion, which is substantially simultaneously dehydrohalhyde and a halogenating agent to give a mixture of ogenated to the substituted styrene product of formula OIIhO- and p a-(haloa ylphenyn e- For example, I. 10 ethyl benzene is converted to oand pchloromethyl The above-described methods are further illustrated phenyl ethane (chloromethylethyl benzene) by reacby the following reactions; tion with hydrogen chloride. These 0- and p- (haloalk- I cu 0 cricri SOC1 CH cucrr CH 0 CH3 1 1) +'C2)'* l 3 2? l CH a CH 3 3 3 CH3 HCl 3 The thionyl chloride and dialkoxy compound used to ylphenyl)ethanes are then further halogenated by a prepare the intermediate compound (1) are present in suitable halogenating reagent. For example, the pabout equal molar quantities. The reaction is carried chloromethylethyl benzene compound above is conout in a reaction medium such as benzene. Any suitable verted to p-chloromethyl( l-bromoethyl)benzene and reaction medium may be used so long as it does not its ortho isomer by bromination. These halogen derivainterfere with the reaction. Other mediums which may tives are then dehydrohalogenated by reaction in a step be used are toluene, xylene, and chloroform. The thio- (2) with an amine acceptor as set out above. nyl chloride is added to a mixture of benzene and 2,6- Preferably, the haloalkylphenyl ethane compound is u e- TO this mixture which has been Stirred is treated with an equimolar amount of the amine accepadded the 1-(3,4-dimethoxyphenyl)ethanol while the t temperature is held at from about 5C to about 20C, Th ub tit t d styrenes f f l II can l b and preferably at about 10C. A thick l rry iS Obtained prepared in a combination process substantially as and heated to about 20C to about 90C and preferably. d ib d above to about soocewhile the above temEeramres are P The above-described methods for preparation of the fi higher of lower tempel'aml'es y also be usedcompounds of formula II are further illustrated by the A filtrate is obtained from which the product is obf ll i reactions;

CICH Cl 1 25 01 (1) I )ClCH .cn CH2 CH3 H C9 01 CHZCI Quint-cs (2) ;(2) I A Q The following examples will further illustrate the process of this invention.

EXAMPLE 1 In a one-liter flask set in an ice bath and equipped with a stirrer, condenser, and dropping funnel were placed 85 gm. (0.8 mole) of 2,6-lutidine and 450 ml of benzene-The mixture was stirred and cooled in the ice bath at 0C, and 39 gm. (0.33 mole) of thionyl chloride were added from the dropping funnel in minutes holding the temperature below 10C. To this stirred mixture were added 60 gm. (0.33 mole) of l-(3,4- dimethoxyphenyhethanol dropwise in one hour, holding the temperature below 10C. The resulting thick slurry was heated slowly to reflux and was maintained at the reflux temperature (80C) for 3 hours. The mixture was stirred overnight at room temperature. In the morning, the insoluble 2,6-lutidine hydrochloride was recovered on a filter. The benzene filtrate was washed with water, a 10% solution of sodium carbonate. and finally again with water. After separation, the benzeneproduct layer was dried over anhydrous sodium sulfate,

and filtered. The solution was stabilized by the addition of 5 gm. of 6-tert-butyl-m-cresol. The mixture was distilled and, after removal of the benzene, the product. 3,4-(dimethoxy)styrene, boiling at l22" 4/9mm. was collected. The product was stabilized was approximately l00ppm. of 6-tert-butyl-m-cres o'l. The yield gm., which is 65% of the theoreticalamoun't of 54 gm.

EXAMPLE 2 In a flask were mixed 2.30 ml. of benzene and 48 gm.

C H (llCl'lO)x HCl C1CH2 EH ca hydrochloride by-product was discarded. The benzene solution was washed twice with water and once with a dilute sodium carbonate solution. It was then heated at reflux over flake sodium hydroxide. The benzene was removed in vacuo, and the residual oil was diluted with ethyl ether. Amine hydrochloride precipitated and was removed by filtration. The filtrate was concentrated to an oil containing 3,4-(dimethoxy)-styrene product, inhibited with a small amount of 2,6-di-tertbutyl-pcresol, and distilled through a short column using an oil vacuum pump. The product was identified by its infrared spectrum. The yield was only 7' gm. or only 15% of its theoretical weight of 46 gm.

The following examples show use of other amine acceptors that can be used in practicing the process of this invention.

EXAMPLES 3-6 In carrying out Examples 3 through 6, the process of Example 2 was conducted with the amine acceptor, pyridine. being replaced by amine acceptors according to this invention. It is to be notedthat the yields are about 3 to 4.5 times greater when an amine acceptor of the invention is used instead of pyridine.

Example Amine Acceptor Yield 3 2.6-lulidine 5 l 7: 4 s-collidine 58% 5 Z-picoline 60% 6 Z-picoline 69% EXAMPLE 7 This example shows how the process can be utilized in the preparation of other substituted styrenes.

Orthoand para-chloromethylstyrenes were prepared in the following manner. Ethyl benzene was chloromethylated with a mixture of para-formaldehyde and hydrochloride to give a ratio of 40 to 60 isomeric mixture of orthoand para-chloromethylethylbenzenes (by nuclear magnetic resonance (NMR) analysis). The yield of the ortho-para mixture was 60-70%.

ca c1 Q 2 Bromination of this mixture gave nearly quantitative yields of p-chloromethyl( l-bromoethyl)benzene and its ortho isomer.

ClCl'l CHBrCl-l The dehydrohalogenation step was carried out by brominating the crude isomeric mixture, isolating it by removing the solvent under vacuum. and treating the brominated isomeric mixture with an equimolar amount (based on theory) of 2.6-lutidine at 90C. The reaction was exothermic, and was considered complete at the end of the exotherm. The reaction mixture was cooled, washed with water and dilute hydrochloric acid, extracted with benzene, and filtered. The benzene was removed by distillation. The crude produce was distilled using a short Vigreaux column at lOO-l50C/ mm. and pure product was obtained in 60% yield. The product was a mixture of ortho and para isomers of chloromethyl styrene in a ratio of 40 to 60% as determined by NMR.

It can be seen from the foregoing that substituted styrenes in highly improved yields can be obtained by the process of this invention. The compounds are useful as monomers for polymerization. Also, 3,4-(dimethoxy)styrene may also be used as an orange juice preservative.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What is claimed is:

l. A method for making a substituted styrene represented by the formula:

R 0 CH=CH wherein each R, is an alkyl radical of l to 4 carbon atoms, comprising:

mixing (i) a halogenating agent selected from thionyl chloride, hydrogen bromide, thionyl bromide, phosphorous tribromide and iodine, (ii) an amine acceptor of the generic formula:

wherein R is an alkyl group of l to 6 carbon atoms, n is an integer having a value of from 1 to 5, and at least one alkyl group is attached to a carbon atom adjacent to the nitrogen atom and when n is more than 1, the alkyl groups may-be the same or difierent groups, and (iii) a l-(3,4-dialkoxyphenyl)ethanol wherein each alkoxy moiety has 1 to 4 carbon atoms, and

heating the resulting mixture for a suflicient period of time and at a temperature sufficient to obtain said substituted styrene.

wherein R is an alkyl group of 1 to 6 carbon atoms, n is an integer having a value of from 1 to 5, and at least one alkyl group is attached to a carbon atom adjacent to the nitrogen atom and when n is more than 1, the alkyl groups may be the same or different groups, v and heating the resulting mixture for a sufficient period of time and at a temperature sufficient to obtain 3,4(dimethoxy)styrene. 6. A method according to claim 5 wherein the amine acceptor is 2,6-lutidine.

7. A method according to claim 5 wherein the amine acceptor is scollidine.

8. A method according to claim 5 wherein the amine acceptor is 2-picoline.

9. A method according to claim 5 wherein substantially equal molar quantities of thionyl chloride and the l-(3,4-dimethoxyphenyl)ethanol are mixed with two molar equivalents of 2,6-lutidine.

10. A method for making 3,4 dimethoxystyrene comprising:

mixing (i) a halogenating agent selected from thionyl chloride, hydrogen bromide, thionyl bromide,

phosphorous tribromide and iodine, (ii) an amine acceptor of the generic formula:

wherein R is an alkyl group of l to 6 carbon atoms, n is an integer having a value of from 1 to 5, and at least one alkyl group is attached to a carbon atom adjacent to the nitrogen atom and when n is more than 1, the alkyl groups may be the same or different groups, and (iii) l-(3,4-dimethoxyphenyl)ethanol, and

heating the resulting mixture for a sufficient period of time and at a temperature sufficient to obtain said 3,4-dimethoxystyrene. 

1. A METHOD FOR MAKING A SUBSTITUTED SYTRENE REPRESENTED BY THE FORMULA:
 2. A method according to claim 1 wherein the amine acceptor is 2,6-lutidine.
 3. A method according to claim 1 wherein the amine acceptor is s-collidine.
 4. A method according to claim 1 wherein the amine acceptor is 2-picoline.
 5. A method for making 3,4-(dimethoxy) styrene comprising the steps of: mixing 1-(3,4-dimethoxyphenyl)ethanol, thionyl chloride, and an amine acceptor of the generic formula:
 6. A method according to claim 5 wherein the amine acceptor is 2,6-lutidine.
 7. A method according to claim 5 wherein the amine acceptor is s-collidine.
 8. A method according to claim 5 wherein the amine acceptor is 2-picoline.
 9. A method according to claim 5 wherein substantially equal molar quantities of thionyl chloride and the 1-(3,4-dimethoxyphenyl)ethanol are mixed with two molar equivalents of 2,6-lutidine.
 10. A method for making 3,4-dimethoxystyrene comprising: mixing (i) a halogenating agent selected from thionyl chloride, hydrogen bromide, thionyl bromide, phosphorous tribromide and iodine, (ii) an amine acceptor of the generic formula: 